Carrier-wave communicating and switching system



Jan. 10,1928.

' E. H. SMYTHE CARRIER wAvE COMMUNICATING AND swITcHING SYSTEM Filed March 12.

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Filed March l2. 1924 17 Sheets-Sheet '7 Jan. 1o, 192a E. H. SMYTHE CARRIER WAVE COMMUNIGATING AND swITcHING SYSTEM .Filed March l2. 1924 '//71/e/7/0f." faW//f /z 50g/Me.

Jan. l0, 1928.

E. H. SMYTHE CARRIER WAVE COMMUNICATING AND SWITCHING SYSTEM Filed March 12. 1924 17 Sheets-Sheet s Jan. 10, 1928. 1,655,520

E. H. SMYTHE CARRIER WAVE COMMUNICATING AND SWITCHING SYSTEM Filed March 12. 1924 l'7 Sheets-Sheet l0 MHH Tl Jan. 10, 1928. 1,655,520

E. H. SMYTHE CARRIER WAVE COMMUNICATING AND SWITCHING SYSTEM.

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Jan. 10, 1928.

' E. H. sMYTHE CARRIER WAVE COMMUNICATING AND SWITCHING SYSTEM Filed March 12. 1924 l'? Sheets-Sheet lg M HI u WES lvmmmm Allmmmmm Jan. 1o, 192s, Q 1,655,520

E. H. SMYTHE CARRIER WAVE COMMUNICATING AND SWITCHING SYSTEM Filed March 12. 1924 1'? sheets-smet 1.3

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E. H. SMYTHE CARRIER WAVE COMMUNICATING AND SWITCHING SYSTEM Filed March l2. 1924 1'? Sheets-Sheet 14 Jan. y10, 1928. 1,655,520

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E. H. SMYTHE CARRIER WAVE COMMUNICATING AND SWITGHING SYSTEMY Filed March l2. 1924 1'? Sheets-Sheet l5 E.,H. sMYTHE CARIER WAVE COMMUNICATING AND SWITCHING SYSTEM Jan. 1o, 192s. y 1,655,520

Filed March 1924 1'? Sheets-Sheet 16 f77 /Z l 5w 302 505 504 wf 505 6fm/ Jan. 10, 1928. 1,655,520

E. H. SMYTHE CARRIER WAVE COMMUNICATING AND SWITCHING SYSTEM Filed March l2. 1924 l? Sheets-Sheet- 17 Patented Jan. 1o, 192s.

UNITED STATI-:s PATENT OFFICE.,

EDWIN H. SMYTHE, oF EvANs'roN, ILLINOIS, AssIGNon To WESTERN ELECTRIC com- PANY, INcoItonATEn, oF NEW YORK, N. YI., A CORPORATION or NEW Yonx.

CARRIER-WAVE COMMUNCATING AND SWTCHING SYSTEM.

Application led March 12, 1924. Serial No. 698,609.

This invention relates to -an. improved interconnecting and communlcatlng system, and morev particularly to a system of the type in which carrler waves or oscillatlons,

' 5 either free or guided, are employed as .the medium for conveying energy for effecting the operation `and control of the electrical switching, signaling and commumcating apr-4 paratus located at separated points 1n the l'lsystem. The invention especially relates to a system in which carrier currents 1n the form of high frequency waves guided upon Wires vare used as the medium of electrical connection between the electrical devices and apparatuses located at Idifferent polnts 1n the system. These carrler currents are assigned such frequencies that they are noninterfering with one another, so that cach carrier serves as a connecting medlum-separate and distinct from the other. carriers superposed upon-the line or medium over which the carriers are transmitted. Each of the carriers is modulated in accordance with the voice currents or other signaling or controlling currents that are to be carried. The carriers thus modulated are transmitted A over the toll or long distance line and are passed through individual arrangement-s each of which is selective of one carrier frequency to the exclusion of the others, and each' of which may have associated with 1t apparat-uses that serve to reproduce from a 4modulated .carrier the voice, signal or controlling currents with which the carrier was modulated at the distant statiom The arrangement which is used to transmit and receive by means of any one high frequency wave as distinguished from that which 1s used for transmitting and receiving by.

40 means of a wave of a different frequency is commonly known as a-high frequency or' carrier channel, or as a frequency selective channel. n

The present invention is directed. partlcularly toward providing a system m which a connection may be established between two or more toll or long distance stations through an intervening switching station or toll center and the carrier multiplex ylines that connect the long distance stations with the toll center, preferably without the necessity of employing manually controlled switching or interconnecting agencies at the intermediate stations, although if desired, as illustrated in one of the modifications of the invention disclosed herein, the interconnecting operation at the switching'` station may be effected by an operator acting under instructions` received from the distant or terminal toll stations; and toward providing a carrier multiplex interconnecting or switching system 1n which the switching or interconnecting of a channel of one line with a channel of a desired one of the other lines 'may be e'ected merely by the shifting of the carrier frequencies of the two channels at the intermediate station, and without the inclusion of any movable switch or relay tive relation with any other channel of the same group; but which are able when the proper frequency shifting operations occur under the control of the operators at the distant toll stations, or if desired, under the control of an operator at the switching station, to afford operative connection in any combination desired between the various channels that center in each group, and therefore between the various lines which these channels represent.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which Fig. 1 is a schematic illustration of. a carrierl multiplex switching system organized in accordance with the principles of the present invention; Figs. 2 to 14, inclusive, taken'together andarrangedin the mannerindicated in Fig. 16 show in as much detail as is necessary'for understanding them the circuits of the complete onganization that is illustrated schematically in Fig. 1. Figs. 2 and 3, 5 and 6, 8 and 9 and 11 and 12 'illustrate the organization of the system at stations 1, 2, 3 and 4, respectively, of the system; Figs.. 4, 7, 10 and 13 illustrate, respectively, the organization of the four switching or interconnecting groups at the switching station, and Fig. 14 shows the apparatus at the switching station for producing the demodulating and channel matching frequencies and for modulating certain of the frequencies with a busy tone in connection wit-h the production and transmission of a return busytest signal. Fig. 15 shows an alternative arrangement for preventing feed-back between the incoming channel branches of a switching group. Figs. 17 and 18 show a modified forni of the invention. In this arrangement instead of the interconnection of the channels being cont-rolled by the operators at the distant terminal toll stations, means are provided at the central switching station whereby they are interconnected by keys controlled by an operator thereat under instructions from a distant toll operator.

The circuit elements out of which the system illustrated in the drawings is built up are the same throughout the entire organization. and are all represented in any one of the four. circuit groups comprised .in Figs. 2, 3- and 4, Figs. 5, 6 and 7, Figs. 8, 9 and 10, or Figs. 11, 12 and 13. But the relationship between the circuit elements at each `of the four stations of the system and in each of the'four interconnecting groups at the switching station differ sufficiently from each other in each station group and in each switching group so that it has seemed desirable to show all of the groups in order that a clear understanding of the system organization may be obtained. These differences in circuit relationship resulting from the association of the elements in a corn lete switching system will be explained in t e detailed description of the invention that is to follow.

The manner in which, in the present embodiment of the invention, the high frequency channels of the carrier multiplex toll lines are associated with each other at the switching station is illustrated in Fig. 1 of the drawing. As schematically illustrated there are four toll stations, station 1, station 2, station 3 and station 4, respectively, and a switching station in which the lines from the four toll stations center or converge. Each of the lines has superposed upon it four high frequency channels, which are designated in the drawing C-l, C-2, C-3 and C-4, respectively. At the switching station the sixteen channels of the four toll lines are associated for switching purposes in four groups designated group 1, group 2,.

group 3 and group 4, respectively. Each of the channels has two branches, one for transmitting in one direction and the other for transmitting in the opposite direction. The direction of transmission in these branches is indicated by the arrows associated with them. Each of the toll lines from the four outlying stations has a different channel associated with each of the four switching groups. Group 1 includes channel 1 of station 1, channel 2 of station 2, channel 3 of station 3 and channel 4 of station 4. Group 2 includes channel 2 of station 1, channel 3 of station 2, channel 4 of station 3 and channel 1 of station 4. Group 3 includes channel 3 of station 1, channel 4 of station 2, channel 1 of station 3 and channel 2 of station 4. Group 4 includes channel 4 of station 1, channel 1 of station 2, channel 2 of station 3 and channel 3 of station 4. Each ,fof the four channels centering in each group "1s adapted to operate at a frequency ditl'erent from the frequencies of the other three channels of the same group; and therefore, although all four lines represented by their respective channels in each groupl are physically connected with each other within the switc ling group, they are normally not operatively connected. The operative connection of one line with another within the group is effected by shifting the frequenc of the receiving or incoming channel branc i of one of the two lines that are to be interconnected to match the frequency at which the outgoing or transmitting branch ot' the other line lis adapted to operate, and by shifting the frequency of the incoming channel branch of the other two lines to match the frequency at which the outgoing branch of the firstV mentioned line is adapted to operate. The manner in which this is accomplished will be explained in the detailed description that is to follow.

The frequency shifting or changing of the incoming channel branches that are to be interconnected inthe switching group is effected under the control of certain lower controlling frequencies that arel applied at the outlying or toll stations as a modulation of the carrier wave transmitted over each channel. Thus, as indicated in Fig. 1 of the drawing, the application of a modulating frequency of 7 5 cycles per second to any of the four channels terminating at station 1 causes a frequency shifting at the switching station that results in the channel of station 1 to which the .modulation is applied being matched or connected with the channel of the corresponding group that is associated with station 2. The application of a modulating frequency of 150 cycles to any ot the channels at station 1 causes the operative connection of the station 1 channel with the station 3 channel of the corresponding switching group; and the application of the 225 cycle modulating frequency to a channel at station 1 causes that channel to be operatively connected in its corresponding switching group with the channel of that group associated with station 4. Similarly at station 2 the application of 225 cycles to a channel causes it to be operativLely connected with a channel extending to station 1; the application of the 7 5 cycle frequency results 1n interconnection with a channel extending lle modulation results in interconnection with station 4. At `station 4 theapplication `of the cycle modulation results in interconnection with station 1; the application of the 150 cycle modulation results in interconnection with station 2; andthe application of the 225 cycle modulation results in interconnection with station 3. At each station the application of a particular one of the three modulating frequencies to any `one ot the channels terminating in that station causes that channel to be interconnected with a particular corresponding one of the other three stations, regardless of the channel to which the modulating frequency is applied and regardless of the particular one of the four switching station groups through which the interconnecting operation is effected.

The application of a particular modulating frequency to a channel not only causes the selective interconnection of that channel with a channel of the desired line in the switchingr station interconnecting group, but it also -identifies at the called station the particular one of the other three stations which is calling. Thus the presence of the 225 cycle modulation upon the receiving branch of any of the channels at station 1 identities the calling station as station 2; the presence of the 150 cycle modulation onfa receiving channel branch atstation 1 identifies the calling station as station 3; and the presence of the 75 cycle modulation identies the callingstation as station 4. At station 2 the presence of the 75 cycle, 225 Cycle orv 150 cycle modulation on the receiving branch of any of the four channels identities the calling station as station 1, station 3 or station 4, respectively; at station 3 the presence of the 15() cycle, 75 cycle or 225 cycle modulation on the receiving branch of any of the channels identifies the calling station'as station 1, station 2 or station 4, respectively; and. at station 4 the presence of the 225 cycle, v150 cycle or 75 cyclemodu'lation on the receiving branch of any of the channels identifies the calling station as station 1, station 2 or stai tion 3- respectively.

In the particular embodiment of the invention that is illustrated schematically in Fig. 1, I have indicated generally the relationships that preferably exist when the system comprises four stations and carrier multiplex lines each with four frequency selective channels arranged for interconnection through the medium of four switching groups at the* central or switching station. Of course, it will be understood that the principles of the invention are readily applicable to switching system ,arrangements wherein the number of carrier multiplex lines, the number of frequency selective channels vsupei-posed upon each line and the number of interconnecting groups at the switching station differ from those in the organization illustrated herein, which may be regarded merely as exemplary. y

The general plan tif-organization of the Vsystem will -now be described more in detail by reference to Figs. 2 to 13, inclusive, of the drawing. rlllie fre uency selective channels associated ywith t e carrier multiplex lines extending to stations 1, 2, 3 and 4 are shown, respectively, in Figs. 3, 6, 9 and 12 of the drawing, and the spring ack terminations of the channels at the four stations are shown in Figs. 2, 5, 8 and 11, respectively. The four interconnecting or switching groups at the switching station are shown in Figs. 4f, 7, 10 and 13, respectively. The springj ack termination of the channels at the various stations is preferred on account of the simplification which it permits in'circuit organization and system operation; but of course it will be understood that the channels may be otherwise terminated in accordance with the well understood practices of the art in case it should be desired to do so. Referring particularly to Fig. 2 as illustrative of the scheme of channel termination that is followed at all of the stations of the system, the springjack terminals are divided into an incoming group and an outgoing group, each of the groups-being provided with as many springjacks per channel as there are distant stations with which interconnect-ion may be had over that channel. Thus, as shown in Fig. 2, inasmuch as there are three distant stations with which each channel may be interconnected there are three spriiigjacks in each of the two mainl groups for each of the four channels terminating in station 1; that is there are four sets of three springjacks each in the incoming group and four sets of three spring'jacks each in the outgoing group.

.Each spriugjack in each group has associated with it asignal or lamp, the lamps associated with the respective springiacks in the incoming group being calling signals,

and the lamps associated with the springjacks in the main outgoing group being busy signals. In vthe preferred form herein illustra-ted the twelve springjacks and lamps lin each of thema-in groups are divided into Vfour lvertical rows corresponding with the four switching groups with which the channels are associated at the switching station, and into three horizontal rows corresponding with the three distant toll stations with which interconnection may be hadthrougli the medium of the four switching groups. At station 1, when station 2 is to be called, the toll plug TP of a pair of connecting cords, such as that illustrated at the left hand side of Fig. 2, is inserted into one or 

